| Pleuronectiformes Soleoidei includes family Soleidae and family Cynoglossidae. There are 31 genus and 120 species in family Soleidae, and there are 3 genus and 127 species in Cynoglossidae. Some scholars have studied phylogenetic relationship of Soleidae species based on 16S rRNA gene, 12S rRNA gene and cyt-b gene. Hitherto, it is not reported that similar methods have been used in phylogenetic analysis of Cynoglossidae species.In this study, phylogenetic relationship of 7 Soleoidei species are analysed by sequence variation of both 16S rRNA gene and COI gene. PCR amplification products of 525bp and 633bp for each gene are obtained and sequenced. Subsequently, these sequences are aligned using Clustal X with Jenkinsia lamprotaenia as outgroup. Basepair composition and sequence variation were examined accordingly. One hundred and seventy three variation sites were detected in 7 Soleoidei species, and 201 variation sites were detected in Cynoglossidae species. The percentage of variable positions within the 633bp partial sequence of COI gene (31.75%) is higher than that within the 525bp partial sequence of 16S rRNA gene (23.05%). Apparently, COI gene has a higher resolution compared with 16S rRNA gene as a phylogenetic marker at least in Soleoidei phylogeny. The average genetic distances of 16S rRNA gene between species, subgenus and genus are 0.0892, 0.1739, 0.1621 while that of COI gene are 0.1182 , 0.2223 , 0.2190 respectively. That is to say, the average intergeneric distance is irregularly smaller than genetic distance among subgenus, as suggests it is possible that family Cynoglossidae may be classified to much more taxa on the base of current classification. Moreover, the interspecific distance of Cynoglossus(Areliscus) abbreviates and C.(A.)purpureomaculatus calculated according to site variations of 16S rRNA gene and COI gene are 0.0021and 0.0016 respectively, while average intraspecific genetic distance according sequence of the two genes are 0.0011 and 0.0016. As a result, it is too close between interspecific and intraspecific distance to distinguish Cynoglossus(Areliscus)abbreviatus and C.(A.)purpureomaculatus merely by analyzing either 16S rRNA gene or COI gene.However, it is of a little arbitrary to characterize them as the same specie on account of the subtle distinction on morphology.Phylogenetic trees are constructed with J.lamprotaenia as outgroup using UPGMA, NJ, ME and MP methods respectively. From both 16S rRNA gene dendrogram and COI dendrogram, it can be clearly seen that 4 species of Cynoglossus(A.) cluster in the same clade with Paraplagusia(Rhinoplagusia) japonica and then, all of them put together, group with C. (Cynoglossus) sinicus. This result also supports the suggestion that there may be more genus or subgenus taxa in Cynoglossidae than current agreement. In general, 16S rRNA gene and COI gene are useful tools for phylogenetic analysis of Soleoidei fishes at the level of species or higer-level, whereas it is not convictive enough for them to distinguish morphologically closely related species and phylogenetic marker with higher resolution should be further developed.Complete sequence of Zebrias zebra mtDNA control region is amplified and compared with sequences of Hippoglossoides reinhardtius and Paralichthys olivaceus downloaded from GenBank. In analogy, the conserved regions of these three species are identified as ETAS, CSB-D, CSB-F, CSB-E, GTGGG-box, CSB-2 and CSB-3. The sequences of CSB-D and GTGGG-box are stringently conserved while a few site variations are found in other regions among species. The function of these regions is still in the Pandora's Box. |
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